Halogenated organosilicon electrolytes, methods of using them, and electrochemical devices containing them

ABSTRACT

Described are electrolyte compositions having at least one salt and at least one compound selected from the group consisting of: 
     
       
         
         
             
             
         
       
         
         
           
             wherein “a” is from 1 to 3; “b” is 1 or 2; 4≧“a”+“b”≧2; X is a halogen; R can be alkoxy or substituted alkoxy, among other moieties, and R 1  is alkyl, substituted alkyl, aryl, substituted aryl, alkoxy, or substituted alkoxy. Also described are electrochemical devices that use the electrolyte composition.

BACKGROUND

A variety of primary batteries employ electrolytes with organic solventssuch as diethyl carbonate (DEC) and ethylene carbonate (EC). Thesebatteries are often stored for extended periods of time before use.However, the performance of these batteries often drops after thisstorage. For instance, the capacity of these batteries often decreasesafter extended storage. Additionally, the pulsing capability of thesebatteries can drop after storage.

Rechargeable lithium batteries are widely discussed in the literatureand are readily commercially available. They typically consist of apositive electrode and a negative electrode spaced by a separator, anelectrolyte, a case, and feedthrough pins respectively connected to theelectrodes and extending externally of the case. Each electrode istypically formed of a metal substrate that is coated with a mixture ofan active material, a binder, and a solvent. In a typical batterydesign, the electrodes comprise sheets which are rolled together,separated by separator sheets, and then placed in a prismatic case.Positive and/or negative feed through pins (i.e., terminals) are thenconnected to the respective electrodes and the case is sealed.

The negative electrode is typically formed of a copper substratecarrying graphite as the active material. The positive electrode istypically formed of an aluminum substrate carrying lithium cobaltdioxide as the active material. The electrolyte is most commonly a 1:1mixture of EC:DEC in a 1.0 M salt solution of LiPF₆. The separator isfrequently a micro porous membrane made of a polyolefin such as acombination of polyethylene and/or polypropylene.

The demand for lithium batteries has increased enormously in recentyears. This increased demand has resulted in ongoing research anddevelopment to improve the safety and performance of these batteries.The conventional organic carbonate solvents employed in the electrolytesof many lithium ion batteries are associated with a high degree ofvolatility, flammability, and chemical reactivity. A variety ofelectrolytes that include polysiloxane solvents have been developed toaddress these issues.

Electrolytes that include a polysiloxane solvent typically have a lowionic conductivity that limits their use to applications that do notrequire high rate performance. Additionally, batteries that includeconventional polysiloxane solvents have shown poor cycling performancewhen used in secondary batteries. As a result, lithium bis-oxalatoborate (LiBOB) has been used as the salt in these electrolytes. WhileLiBOB improves the performance of the batteries, LiBOB is unstable inthe presence of water. The amount of moisture in battery electrolytesand/or electrodes can be on the order of several hundred ppm. Thepresence of this moisture can cause LiBOB to decompose into lithiumoxalate (LiHC₂O₄.H₂O) and form a precipitate in the electrolyte. Thisprecipitate tends to increase the internal resistance of electricaldevices such as batteries.

Thus there remains a long-felt and unmet need to increase theperformance, safety, and storage life of lithium-based batteries andother electrical charge-storing devices.

SUMMARY OF THE INVENTION

Disclosed herein is an electrolyte composition comprising at least onesalt and at least one compound selected from the group consisting of:

wherein subscript “a” is an integer of from 1 to 3;

subscript “b” is 1 or 2; and

4≧“a”+“b”≧2;

X is a halogen;

R is selected from the group consisting of alkoxy, substituted alkoxy,Formula 1 moieties, and Formula II moieties:

wherein R² is an organic spacer;

R₃ is nil or an organic spacer;

R⁴ is hydrogen, alkyl, or aryl;

R⁵ is alkyl or aryl;

subscript “c” is 1 or 2; and

subscript “d” is from 1 to 12; and

R¹ is selected from the group consisting of alkyl, substituted alkyl,aryl, substituted aryl, alkoxy, and substituted alkoxy.

In one version of the electrolyte composition X is chlorine, fluorine,or bromine. In another version of the electrolyte composition, X isfluorine. In certain versions of the electrolyte composition, “a” is 1,“b” is 1, and R¹ is C₁ to C₁₀ alkyl. In still other versions of theelectrolyte composition, R¹ is methyl.

In yet another version of the composition, R is substituted orunsubstituted lower alkoxy, and R¹ is substituted lower alkyl or loweralkoxy.

In any version of the composition described herein, at least one saltmay be a lithium-containing salt. At least one salt may be present in aconcentration of from about 0.1 M to about 3.5 M. Concentrations aboveand below 0.1 M to 3.5 M are explicitly within the scope of thecomposition described and claimed herein.

In any version of the composition described herein, at least one saltmay be selected from the group consisting of LiClO₄, LiBF₄, LiAsF₆,LiPF₆, LiCF₃SO₃, Li(CF₃SO₂)₂N, Li(CF₃SO₂)₃C, Li(C₂F₅ SO₂)₂N, LiDFOB,LiBOB, lithium alkyl fluorophosphates, lithium borates and lithiumbis(chelato)borates. Other salts are within the scope of the compositiondescribed and claimed herein. This list is by way of example only andnot limitation.

The electrolyte composition may be a liquid, a gel, or a solid.

Also described herein is an electrochemical device characterized in thatit includes an electrolyte composition as recited as described andclaimed herein. The electrochemical device may include an anode and theelectrolyte composition may further be characterized in that it forms apassivation layer on the anode. In one version, the device is a lithiumsecondary battery comprising at least one lithium metal oxide cathodeand at least one anode.

The compounds described herein are also part of the invention. Thus,disclosed herein are compounds selected from the group consisting of:

wherein subscript “a” is an integer of from 1 to 3; subscript “b” is 1or 2; and 4≧“a”+“b”≧2; X is a halogen; R is selected from the groupconsisting of alkoxy, substituted alkoxy, Formula 1 moieties, andFormula II moieties:

wherein R² is an organic spacer; R₃ is nil or an organic spacer; R⁴ ishydrogen, alkyl, or aryl; R⁵ is alkyl or aryl; subscript “c” is 1 or 2;and subscript “d” is from 1 to 12; and R¹ is selected from the groupconsisting of alkyl, substituted alkyl, aryl, substituted aryl, alkoxy,and substituted alkoxy.

Numerical ranges as used herein are intended to include every number andsubset of numbers contained within that range, whether specificallydisclosed or not. Further, these numerical ranges should be construed asproviding support for a claim directed to any number or subset ofnumbers in that range. For example, a disclosure of from I to 10 shouldbe construed as supporting a range of from 2 to 8, from 3 to 7, 5, 6,from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, and so forth.

All references to singular characteristics or limitations of the presentinvention shall include the corresponding plural characteristic orlimitation, and vice-versa, unless otherwise specified or clearlyimplied to the contrary by the context in which the reference is made.

All combinations of method or process steps as used herein can beperformed in any order, unless otherwise specified or clearly implied tothe contrary by the context in which the referenced combination is made.

The methods of the present invention can comprise, consist of, orconsist essentially of the essential elements and limitations of themethod described herein, as well as any additional or optionalingredients, components, or limitations described herein or otherwiseuseful in synthetic organic chemistry.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a reaction scheme depicting how to make one of the preferredorganosilicon compounds. As depicted, the compound F1S3M3 includes asilicon atom to which is bonded a fluorine (F1), two methyl groups, atrimethylene spacer (S3), and three (3) polyethylene oxide units intandem (M3).

FIG. 2 is a graph depicting the synthesis of F1S3M2, a homolog of theF1S3M3 compound depicted in FIG. 1. As shown in FIG. 2, the compoundF1S3M2 includes a silicon atom to which is bonded a fluorine (F1), twomethyl groups, a trimethylene spacer (S3), and two (2) polyethyleneoxide units in tandem (M2).

FIGS. 3A and 3B are graphs depicting the thermal stability of 1NM3 (FIG.3A) and F1S3M2 (FIG. 3B). As noted in the figure, F1S3M2 displayed lessthan 5% decomposition after heating to 150° C. in the present of 1MLiPF₆.

FIG. 4 is a graph depicting half cell cycling performance of compoundF1S3M3 as shown in FIG. 1, at 70° C., using a NMC cathode. The X-axisrecords cycle number, the Y-axis records specific capacity in mAh/g. Thespecifics of the charge-discharge cycle and anode/cathode constructionare recorded at the bottom of the figure. (“NMC”=Nickel MagnesiumCobalt; “CCCV”=constant current, constant voltage. NMC cathodes areavailable from many commercial suppliers, such as Targray Inc., LagunaNiguel, Calif., USA; “W-Scope” film is a commercial, proprietaryseparator sold by W-Scope Corporation, Kawasaki, Japan.)

FIG. 5 is a graph depicting half cell cycling performance of compoundF1S3M3 at 70° C. using a NCA cathode. The X-axis records cycle number,the Y-axis records specific capacity in mAh/g. The specifics of thecharge-discharge cycle and anode/cathode construction are recorded atthe bottom of the figure. (“NCA”=Nickel Cobalt Aluminum. NCA cathodesare commercially available from numerous sources, including Targray Inc.“Celgard 2400” is a monolayer polypropylene-based separator availablecommercially from Celgard LLC, Charlotte, N.C., USA.)

FIG. 6 is a graph depicting full cell cycling performance of compoundF1S3M3 at 70° C. using a NMC cathode. The X-axis records cycle number,the Y-axis records specific capacity in mAh/g. The specifics of thecharge-discharge cycle and anode/cathode construction are recorded atthe bottom of the figure. (“EC”=ethylene carbonate; “DEC”=diethylcarbonate.)

FIG. 7 is a graph depicting full cell cycling performance of F1S3M2 at70° C. using a NCA cathode. The X-axis records cycle number, the Y-axisrecords discharge capacity in mAh.

FIG. 8 is a graph depicting full cell cycling performance of F1S3M2 at55° C. using a NCA cathode. The X-axis records cycle number, the Y-axisrecords discharge capacity in mAh. This graph compares using EC:DEC asthe electrolyte versus 78% F1S3M2/20% EC/1M LiPF₆.

FIG. 9 is a graph comparing discharge rates at 30° C. between F1S3M2 ascompared to carbonate using a NCA cathode. As noted in the figure, thetwo are indistinguishable.

DETAILED DESCRIPTION

The present disclosure relates to an electrolyte composition containingat least one halogenated organosilicon solvent, and an electrochemicaldevice characterized by including the electrolyte composition. Thepreferred electrochemical device is a lithium secondary batterycomprising the electrolyte composition described herein. Morespecifically, described herein is an electrolyte composition that ismoisture-resistant, non-flammable, has a wide temperature-operationwindow, and is far safer as compared to conventional electrolytes.Moreover, the electrolyte composition disclosed herein has improvedcapacity retention properties, voltage stability and durability whenincorporated into a lithium secondary battery or other lithium-ioncharge storage devices.

It has been discovered by the named co-inventors that fluorinatedorganosilicon compounds are non-hydrolyzable at room temperature. Thus,the resulting electrolytes have a much higher tolerance for moisture.Simultaneously, the voltage stability of the organosilicon compoundsdescribed herein is greatly improved, presumably due to the effect ofhalogen substitutions. The electrolyte compositions described herein,which are halogenated organosilicon solvents (generally liquids, but canalso be solid) are non-flammable, offer improved safety and highervoltage windows than conventional electrolytes, and provide a uniquesolid electrolyte interphase (SEI) film on the graphite anode, resultingin better performance and cell capacity. Cells using the electrolytecompositions described herein improve capacity retention, voltage andthermal stability, and can be operated over a wide temperature window -most notably at elevated temperatures.

As used herein, the term “alkyl,” by itself or as part of anothersubstituent, means, unless otherwise stated, a fully saturated,straight, branched chain, or cyclic hydrocarbon radical, or combinationthereof, and can include di- and multi-valent radicals, having thenumber of carbon atoms designated (e.g., C₁-C₁₀ means from one to tencarbon atoms, inclusive). Examples of alkyl groups include, withoutlimitation, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl,isobutyl, sec-butyl, cyclohexyl, (cyclohexyl)ethyl, cyclopropylmethyl,and homologs, and isomers thereof, for example, n-pentyl, n-hexyl,n-heptyl, n-octyl, and the like. The term “alkyl,” unless otherwisenoted, also includes “cycloalkyl.”

The term “alkenyl” means an alkyl group as defined above containing oneor more double bonds. Examples of alkenyl groups include vinyl,2-propenyl, crotyl, 2-isopentenyl, 2-butadienyl, 2,4-pentadienyl,1,4-pentadienyl, etc., and higher homologs and isomers.

The term “alkynyl” means an alkyl or alkenyl group as defined abovecontaining one or more triple bonds. Examples of alkynyl groups includeethynyl, 1- and 3-propynyl, 3-butynyl, and the like, including higherhomologs and isomers.

The terms “alkylene,” “alkenylene,” and “alkynylene,” alone or as partof another substituent means a divalent radical derived from an alkyl,alkenyl, or alkynyl group, respectively, as exemplified by—CH₂CH₂CH₂CH₂—.

Typically, alkyl, alkenyl, and alkynyl groups (as well as alkylene,alkenylene, and alkynylene groups) will have from 1 to 36 carbon atoms,although longer alkyl groups are explicitly within the scope of the term“alkyl.” Those groups having 10 or fewer carbon atoms in the main chainare preferred in the present compositions, and groups of this length arecollectively referred to as “lower alkyl, “lower alkenyl,” etc.

The term “alkoxy” is used herein to refer to the —OR group, where R isan alkyl as defined herein or a substituted analog thereof. Suitablealkoxy radicals include, for example, methoxy, ethoxy, t-butoxy, etc. Inthe same fashion as “lower” with respect to alkyl, “lower alkoxy” refersto an alkoxy group of 10 or fewer carbon atoms in the main chain.

“Substituted” refers to a chemical group as described herein thatfurther includes one or more substituents, such as lower alkyl, aryl,acyl, halogen (e.g., alkylhalo such as CF₃), hydroxy, amino, alkoxy,alkylamino, acylamino, thioamido, acyloxy, aryloxy, aryloxyalkyl,mercapto, thia, aza, oxo, both saturated and unsaturated cyclichydrocarbons, heterocycles and the like. These groups may be attached toany carbon or substituent of the alkyl, alkoxy, and aryl moieties.Additionally, these groups may be pendent from, or integral to, thecarbon chain itself.

The term “acyl” is used to describe a ketone substituent, —C(O)R, whereR is substituted or unsubstituted alkyl or aryl as defined herein. Theterm “carbonyl” is used to describe an aldehyde substituent. The term“carboxy” refers to an ester substituent or carboxylic acid, i.e.,—C(O)O— or —C(O)—OH.

The term “aryl” is used herein to refer to an aromatic substituent,which may be a single aromatic ring or multiple aromatic rings which arefused together, linked covalently, or linked to a common group such as adiazo, methylene or ethylene moiety. The common linking group may alsobe a carbonyl as in benzophenone. The aromatic ring(s) may include, forexample phenyl, naphthyl, biphenyl, diphenylmethyl and benzophenone,among others. The term “aryl” encompasses “arylalkyl” and “substitutedaryl.” For phenyl groups, the aryl ring may be mono-, di-, tri-, tetra-,or penta-substituted. Larger rings may be unsubstituted or bear one ormore substituents.

“Substituted aryl” refers to aryl as just described including one ormore functional groups such as lower alkyl, acyl, halogen, alkylhalo(e.g., CF₃), hydroxy, amino, alkoxy, alkylamino, acylamino, acyloxy,phenoxy, mercapto, and both saturated and unsaturated cyclichydrocarbons which are fused to the aromatic ring(s), linked covalentlyor linked to a common group such as a diazo, methylene, or ethylenemoiety. The linking group may also be a carbonyl such as in cyclohexylphenyl ketone.

“Halogen” or “halo” refers to the elements of Group 17 (IUPAC-style)(formerly group VII or VIIA) of the periodic table, namely fluorine (F),chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

The term “organic spacer” or “spacer” refers to a divalent groupincluding alkylene, alkenylene, and alkynylene groups. Other suitablespacers include alkylene oxide, and bivalent ether moieties. Thesespacers can be substituted or unsubstituted. The above spacers can alsobe completely or partially halogenated. For instance, the spacers can becompletely or partially fluorinated.

The electrolyte compositions comprise at least one salt and at least onecompound selected from the group consisting of:

wherein subscript “a” is an integer of from 1 to 3; subscript “b” is 1or 2; and 4>“a”+“b”≧2. X is a halogen. R is selected from the groupconsisting of alkoxy and substituted alkoxy. R may also be a moietyselected from Formula 1 and/or Formula II:

wherein R² is an organic spacer; R³ is nil or an organic spacer; R⁴ ishydrogen, alkyl, or aryl; R⁵ is alkyl or aryl; subscript “c” is 1 or 2;and subscript “d” is from 1 to 12.

R¹ is selected from the group consisting of alkyl, substituted alkyl,aryl, substituted aryl, alkoxy, and substituted alkoxy.

It is preferred that X is chlorine, fluorine, or bromine, mostpreferably fluorine. When X is fluorine, it is also preferred that “a”is 1, “b” is 1, and R¹ is C₁ to C₁₀ alkyl (and most preferably R¹ ismethyl). In certain preferred embodiments of the composition, R issubstituted or unsubstituted lower alkoxy, and R¹ is substituted loweralkyl or lower alkoxy.

Particularly preferred silicon-containing compounds according to thepresent disclosure are:

wherein X is Cl, Fl, or Br. Most preferred are those in which X isfluorine, and the C₁₋₁₀ alkyl groups are C₆ or smaller (and mostpreferably methyl). The preferred silicon-containing compounds aredesignated F1S3M3, and F1S3M2; F1S3M3 is depicted in FIG. 1.

It is preferred that the salt be a lithium-containing salt. From amongthe lithium-containing salts, LiClO₄, LiBF₄, LiAsF₆, LiPF₆, LiCF₃SO₃,Li(CF₃SO₂)₂N, Li(CF₃SO₂)₃C, Li(C₂F₅ SO₂)₂N, LiDFOB, LiBOB, lithium alkylfluorophosphates, lithium borates and lithium bis(chelato)borates arepreferred. If a lithium salt is used, preferably it is present in thecomposition in a concentration of from about 0.1 M to about 3.5 M.Concentrations above and below this stated range are explicitly withinthe scope of the present disclosure. The composition is preferablyformulated to be a free-flowing liquid. However, the electrolyte mayalso be formulated to be a gel or a solid, depending upon the moietiesselected for R and R¹ and the concentration of the silicon-containingcompound in the electrolyte composition as a whole.

The present disclosure includes any and all electrochemical devices thatcomprise the electrolyte composition described and claimed herein. Suchdevices may optionally comprise an anode and the electrolyte compositionoptionally further comprises an additive dimensioned and configured toform a passivation layer on the anode. Preferred electrochemical devicesare lithium secondary batteries that comprise at least one lithium metaloxide cathode and at least one anode.

Synthesis of F1S3M3:

Depicted in FIG. 1 is the preferred silicon-containing compound, whichhas been designated F1S3M3.

The synthesis begins with the triethyleneglycol allyl methyl ether(“TEGAME”). This is a known and common compound that can be made byseveral literature routes, most of which involve adding the allyl groupto the glycol using allyl bromide under different conditions, and usingdifferent solvents, temperatures, times, and bases. The route used herewas as follows (illustrated in Scheme 1, below):

Triethyleneglycol methyl ether (185 mL) was dissolved in 500 mL oftoluene and 47.2 g of NaOH were added under vigorous stirring in a 1Lflask. When the mixture was homogenous, 143 g of allylbromide was addeddrop-wise using an addition funnel over a two hour period. Care wastaken to ensure that the mixture did not get too hot. (If the solutionboils, the concentration of allylbromide drops.) After the two-houraddition, the mixture was kept at about 50° C. overnight. The next daythe liquid was decanted and the solid washed with hexane. The liquidfractions were mixed and the solvents (hexane and toluene) wereevaporated by rotary evaporation. The crude orange product was vacuumdistilled (about 85° C. at 0.5 Torr) to give the intermediate product,the triethyleneglycol allyl methyl ether.

The next step involved the synthesis of the disiloxane 2S3D3 using ahydrosilylation reaction. See FIG. 1. This synthesis can also beaccomplished under different conditions and using different catalysts.The route used here was as follows:

Triethyleneglycol allyl methyl ether (185 mL) was mixed with 66 g of1,1,3,3-tetramethyldisiloxane and added approximately 100 uL ofplatinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solutionin xylene, Pt=2%. This was stirred at room temperature, with care takenthat the solution did not boil. The mixture was then heated to about 50°C. overnight. In some runs, the disiloxane 2S3D3 was distilled (˜240°C.; 1 Torr). In other runs, the disiloxane was used without furtherpurification. See Scheme 2:

The Si—O—Si bond in 2S3D3 is then substituted with a halogen, in thisexample, fluorine. This can be done using LiPF₆, NaF, NH₄F, NH₄FHF, andthe like. Any analogous halogen-containing compound (i.e., containing Clor Br, rather than F) can be used.

265 g of 2S3D3 were mixed with 37 g of LiPF₆ and the mixture stirred todissolve the salt. Then 4.5 g of water were added and the mixture wasstirred overnight. The solution was then heated to about 80° C. forthree hours to make it homogenous. The crude dark mixture was distilledthree times to get pure F1S3M3. See FIG. 1 and Scheme 3:

This same set of reactions can be used to make analogous compounds byusing longer or shorter glycol units in Scheme 1, and altering theterminal moieties in the starting ether. Likewise, in Scheme 2, the1,1,3,3-tetramethyldisiloxane can be replaced with other disiloxaneshaving a distinct substitution pattern, for example, different alkyllengths, alkyloxy groups, etc. In the same fashion, thehalogen-containing compound used to replace the Si—O—Si bond in 2S3D3dictates the halogen atom that appears in the final product.

For example, see FIG. 2, which describes the analogous preferredsynthesis of F1S3M2. Here, the initial hydrosilylation step takes placeover a platinum catalyst to yield a chlorinated intermediate. The chlorointermediate is then treated with NH₄FHF (ammonium bifluoride) to yieldthe product F1S3M2 in good yield.

All analogous compounds as recited above can be fabricated using thesynthetic approach presented in FIGS. 1 and 2 and using the appropriatestarting material to arrive at the desired chain length of the spacer(R² and/or R³), the desired side groups R and R¹, and the desiredhalogen X. In addition, one skilled in the art will recognize thatalternate routes from reagents such as Me₂SiHF are equally viable.

Of particular note is that the compositions described herein have muchimproved thermal stability as compared to other Si-containingelectrolytes such as 1NM3. See FIGS. 3A and 3B, which are graphsdepicting the thermal stability of 1NM3 (FIG. 3A) versus the stabilityof F1S3M2 (FIG. 3B). (“1NM3”=(CH₃)₃—Si—O—(CH₂CH₂O)₃—CH₃) As shown inFIG. 3B, F1S3M2 displayed less than 5% decomposition after heating to150° C. in the present of 1M LiPF₆. In stark contrast, as shown in FIG.3A, 1NM3 displayed near-complete (˜100%) at 100° C. in the presence of 1M LiPF₆. FIG. 4 is a graph depicting half cell cycling performance ofcompound F1S3M3 at 70° C., using a NMC cathode. The X-axis records cyclenumber, the Y-axis records specific capacity in mAh/g. The specifics ofthe charge-discharge cycle and anode/cathode construction are recordedat the bottom of the figure. Of particular note in FIG. 4 is the verystrong specific capacity of the F1S3M3 half cell after 50charge/discharge cycles. The specific capacity for the F1 S3M3 half cellafter 50 charge/discharge cycles was still well above 100 mAh/g. Incontrast, the specific capacity of the 1NM3 half cell plummeted to closeto zero after only 15 cycles. While the carbonate control half cellperformed far better than the 1NM3 half cell, its performance wassignificantly worse than the F1S3M3 half cell after about 35charge/discharge cycles.

The performance results were even more dramatic when comparing F1S3M3 at70° C. using NCA cathodes. See FIG. 5. In this set of experiments, thecarbonate control half cell and the F1S3M3 half cell performed innear-parallel fashion. In contrast, the specific capacity of the 1NM3half cell plummeted after approximately 10 cycles. This graph shows thatthe electrolyte composition described herein function quite well usingdifferent types of anodes, cathodes, and separators. Note that the FIG.4 experiments used a half cell constructed of a NMC cathode, a lithiumanode, and a W-Scope film separator. The F1S3M3 half cell performedadmirably. The FIG. 5 experiments used a half cell constructed of a NCAcathode, a lithium anode, and a Celgard 2400 separator. The F1S3M3 halfcell performed admirably under these conditions too.

In full cell cycling (F1S3M3/EC), the compositions according to thepresent disclosure also fared well. See FIG. 5, which is a graphdepicting full cell cycling performance of compound F1S3M3 at 70° C.using a NMC cathode. As shown in the figure, the F1S3M3 full cellequaled the performance of the carbonate control cell under theseconditions. Similar results were obtained for F1S3M2 using a NCAcathode, as shown in FIG. 7. FIG. 7 is also notable because thedischarge capacities followed identical trajectories whether at C/10 orC/2. In short, the electrolyte composition containing F1S3M2 performedin essentially identical fashion to the graphite control and the EC/DECcontrol. (The graph depicted in FIG. 7 shows full cell cyclingperformance of F1S3M2 at 70° C. using a NCA cathode.)

FIG. 8 is similar to FIG. 7, but depicts full cell cycling performanceof F1S3M2 at 55° C. using a NCA cathode. In the same fashion as in FIG.7, the results are virtually indistinguishable between at both C/10 andC/2 as between the full cell containing the F1S3M2 electrolyte versusgraphite control versus EC:DEC control. All results wereindistinguishable. This is notable in that compositions according to thepresent disclosure are able to function at a host of differenttemperature conditions, using different anode and cathode materials, anddifferent separators.

Lastly, see FIG. 9, which is a graph comparing discharge rates at 30° C.between F1S3M2 as compared to EC:DEC control device using a NCA cathode.As is clearly seen in FIG. 9, the discharge capacity of the F1S3M2device closely mirrored that of the EC:DEC device at a host of differentdischarge conditions varying between C/10 to 2C during the course of thecharge-discharge cycling. The results here are very significant in thatthe discharge rate was varied widely in cycles 1 to 8 (C/10, to C/4, toC/2, to C/1, to 2C, to C/10, and then held steady at C/4 from cycle 8 tocycle 17). The device including the electrolyte composition describedherein performed in essentially the same fashion as the controls.

1. An electrolyte composition comprising at least one salt and at leastone compound selected from the group consisting of:

wherein subscript “a” is an integer of from 1 to 3; subscript “b” is 1or 2; and 4≧“a”+“b”≧2; X is a halogen; R is selected from the groupconsisting of alkoxy, substituted alkoxy, Formula 1 moieties, andFormula II moieties:

wherein R² is an organic spacer; R₃ is nil or an organic spacer; R⁴ ishydrogen, alkyl, or aryl; R⁵ is alkyl or aryl; subscript “c” is 1 or 2;and subscript “d” is from 1 to 12; and R¹ is selected from the groupconsisting of alkyl, substituted alkyl, aryl, substituted aryl, alkoxy,and substituted alkoxy.
 2. The electrolyte composition of claim 1,wherein X is chlorine, fluorine, or bromine.
 3. The electrolytecomposition of claim 2, wherein X is fluorine.
 4. (canceled)
 5. Theelectrolyte composition of claim 1, wherein R¹ is methyl.
 6. Theelectrolyte composition of claim 1, wherein R is substituted orunsubstituted lower alkoxy, and R¹ is substituted lower alkyl or loweralkoxy.
 7. The electrolyte composition according to claim 1, wherein theat least one salt is a lithium-containing salt.
 8. The electrolytecomposition according to claim 1, wherein the at least one salt ispresent in a concentration of from about 0.1 M to about 3.5 M.
 9. Theelectrolyte composition according to claim 1, wherein the at least onesalt is selected from the group consisting of LiClO₄, LiBF₄, LiAsF₆,LiPF₆, LiCF₃SO₃, Li(CF₃SO₂)₂N, Li(CF₃SO₂)₃C, Li(C₂F₅ SO₂)₂N, LiDFOB,LiBOB, lithium alkyl fluorophosphates, lithium borates and lithiumbis(chelato)borates.
 10. The electrolyte composition according to claim1, wherein the composition is a liquid.
 11. The electrolyte compositionaccording to claim 1, wherein the composition is a gel.
 12. Theelectrolyte composition according to claim 1, wherein the composition isa solid.
 13. An electrochemical device comprising an electrolytecomposition as recited in claim
 1. 14. The device of claim 13, whereinthe electrochemical device includes an anode and the electrolytecomposition further comprises an additive that forms a passivation layeron the anode.
 15. The device of claim 13, wherein the device is alithium secondary battery comprising at least one lithium metal oxidecathode and at least one anode.
 16. A compound selected from the groupconsisting of:

wherein subscript “a” is an integer of from 1 to 3; subscript “b” is 1or 2; and 4≧“a”+“b”≧2; X is a halogen; R is selected from the groupconsisting of alkoxy, substituted alkoxy, Formula 1 moieties, andFormula II moieties:

wherein R² is an organic spacer; R₃ is nil or an organic spacer; R⁴ ishydrogen, alkyl, or aryl; R⁵ is alkyl or aryl; subscript “c” is 1 or 2;and subscript “d” is from 1 to 12; and R¹ is selected from the groupconsisting of alkyl, substituted alkyl, aryl, substituted aryl, alkoxy,and substituted alkoxy.
 17. A compound of claim 16, wherein X ischlorine, fluorine, or bromine.
 18. A compound of claim 16, wherein X isfluorine.
 19. (canceled)
 20. A compound of claim 16, wherein R¹ ismethyl.
 21. A compound of claim 16, wherein R is substituted orunsubstituted lower alkoxy, and R¹ is substituted lower alkyl or loweralkoxy.